Barrier with superhydrophobic coating

ABSTRACT

A barrier of open pore mesh provided with a superhydrophobic coating to prevent wetting when exposed to an aqueous liquid. The disclosed barrier could be a mesh screen or a liquid pervious membrane. The barrier is useful in a filter media containment to permit egress of gas, usually air, from the containment even when subjected to an aqueous liquid containing environment.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit pursuant to Title 35 USC §119(e) toProvisional Application No. 61/506,227, filed Jul. 11, 2011, the entirespecification and drawings of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

This disclosure relates to a barrier comprising an open pore mesh ormembrane structure with gaseous flow capability for an environmentinvolving the presence of liquid. More particularly, it relates to anopen pore mesh or membrane with gaseous flow capability that isparticularly immune to flow impairment in the presence of aqueousliquid.

Various industrial or commercial applications involve handling fluids ina gaseous and/or liquid state. Often they include selective barriers tofluid flow. That is, process barriers or filters possess the capabilityto permit passage of gas, such as air, but resist consequences ofexposure to liquid such as water. One such configuration involves afilter or barrier that permits passage of gas from a contaminant eventhough exposed to an environment containing aqueous liquid. Thisdisclosure is directed to such a structure with superior properties tomaximize effectiveness.

Open pore mesh configurations are known. Typically, to possesshydrophobic qualities, the pore size must be about 10 microns or less.This configuration is, however, restrictive to air flow. Moreover, ithas also been determined that in an environment involving exposure toaqueous liquid, conventional mesh screen tends to “wet” and therebyclose the pores of the mesh. That is, the surface tension of the liquidcauses it to fill the pores prohibiting passage of gas. In someapplications this problem is particularly prevalent because there isessentially no pressure differential across the barrier to force thegaseous medium through the mesh.

Though numerous and varied applications are contemplated for thestructure of the present disclosure, it is illustrated herein withreference to a specific embodiment for which it is consideredparticularly suitable. It must be understood, however, that theproperties of the structure make it suitable for any applicationinvolving or dependent upon susceptibility to passage of a gaseousmedium, and impervious to the deleterious effect of the presence of anaqueous liquid.

SUMMARY OF DISCLOSURE

The gas pervious barrier of the present disclosure is provided with asuperhydrophobic coating to prevent wetting when exposed to an aqueousliquid. The barrier may be a liquid pervious open pore mesh or amembrane. The barrier is useful in a filter media containment to permitegress of gas, usually air, from the containment even when subjected toa liquid containing environment.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional plan view of a water pitcher with a filterassembly illustrative of the principles of the present disclosure;

FIG. 2 is a cross-sectional plan view of the filter assembly of thewater pitcher of FIG. 1.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

FIG. 1 is illustrative of the particular application of the structure ofthe disclosure to a purification media canister. There is illustrated awater pitcher generally designated 10 with a handle 11 and spout 13. Itdefines separate volumes 12 and 14 separated by a wall 15. Wall 15includes an aperture that retains a removable purification canister 16.The pitcher 10 includes a liquid inlet to volume 12 closed by removablecover 18. Liquid is discharged from the volume 14 of pitcher 10 at spout13. The pitcher 10 and its components may be made of molded plastiSimilarly, the purification canister 16 is a plastic containment.

Untreated liquid is poured into volume 12 through the inlet normallyclosed by cover 18. It passes into volume 14 through purificationcanister 16. Purified liquid is poured out of volume 14 at spout 13using handle 11.

Purification canister 16 is illustrated separately in FIG. 2. Thecanister 16 is elongated and includes generally cylindrical wall 20. Itincludes an upper or inlet end 22 and a lower, or outlet end 23. Ithouses a quantity of purification media 24, usually granular activatedcharcoal.

Cylindrical wall 20 may include a radial flange 26 to limit insertion ofpurification canister 16 into the aperture in dividing wall 15. A sealring 27, seen in FIG. 1, may be employed to provide a fluid tight sealbetween the canister 16 and the dividing wall 15.

Outlet end 23 of canister 15 includes a bottom wall 30 with a pluralityof apertures 31 in fluid communication with volume 14 of pitcher 10.

Inlet end 22 of canister 16 includes a truncated conical wall 32 and acircular planar top wall 34. Truncated conical wall 32 includes aplurality of inlet slots 36. Fluid poured into volume 12 is free to passinto purification canister 16 through inlet slots 36. A mesh screen 38may overlie the slots to prohibit entry of particulate matter or othercontaminants and to retain media 24.

Use of pitcher 10 involves filling the pitcher with liquid poured intovolume 12. The poured liquid, usually water, passes through the inletslots 36 and mesh screen 38 into purification canister 16. The liquidpasses through the media 24 and through apertures 31 in bottom wall 30and into volume 14.

It has been determined that meaningful quantities of gas, usually air,are entrained in the liquid, or created by turbulent flow associatedwith the filing function or released by media 24. It is also deemeddesirable to purge the air from the canister as it often impacts theflow through the filter 16. Toward this objective circular planar topwall 34 is provided with a central or vent opening 40. As illustrated,the opening 40 is covered with a treated mesh screen 42 that permitsgases within the upper end of canister 16 to escape into volume 12,maximizing usefulness of the purification canister.

In accordance with the present disclosure, the mesh screen 42 includes acoating on its exterior surface of superhydrophobic material. Screen 42may be insert molded, heat staked, or ultrasonically sealed or otherwiseassociated with the planar top wall 34. The superhydophobic coating onmesh screen 42 may be applied by any suitable means, such as, forexample, by spin-coating, ink jet printing, blade casting, dip coating,or aerosol spraying prior to, or after, assembly.

The superhydrophobic coating renders the mesh 42 resistant to “wetting”or pore closure due to liquid surface tension. With the central openingin top wall 40 and treated mesh screen 42 in place, air within thepurification canister 16 is free to pass through the pores of thetreated mesh screen 42. Because of the presence of the superhydrophobiclayer on the surface of the mesh 42 exposed to the volume 12 of pitcher10 liquid within the volume 12 or liquid that splashes onto mesh 42during the filling function is prevented from wetting the mesh material.Accordingly, the pores of the mesh remain open and air may readily purgefrom canister 16.

Useful alternatives to the mesh include other forms of filter media suchas woven screen, non-woven screen, or membrane. It is contemplated thatsatisfactory performance can be achieved with a superhydrophobic coatedmesh having a coating of thickness of less than 200 nanometers.

Superhydrophobic coating material is available from Lotus Leaf Coatings,a New Mexico-headquartered corporation licensed to commercializesuperhydrophobic coatings developed at Sandia National Laboratory andthe University of New Mexico. The coating is made up of amorphous silicaand a custom engineered polymer that does not contain fluorine orper-fluoro compounds. The coating from Lotus Leaf Coatings is describedin U.S. Pat. No. 7,485,343, issued Feb. 3, 2009, entitled “Preparationof Hydrophobic Coatings.” The entire disclosure is hereby incorporatedherein by reference as if fully set forth herein. The materialcontemplated will provide a contact angle of a water droplet typicallyexceeding 150° with a roll off angle of less than 10°.

Use of a mesh with a superhydrophobic coating permits use of larger meshsizes, around 40 microns or larger. Such screens or membrane willperform effectively even with the larger pore or mesh opening size. Ithas been found that a coated vent 40 with a screen 42 having a mesh thesize of 160 microns works effectively.

It is recognized that air could under ideal circumstances escapecanister 16 through inlet slots 36. This path, however, is subject torandom closure by quantities of water being poured into volume 12. Thisdisclosure illustrates the advantages of a separate air passage atcentral opening 40 in planar top wall 34. Moreover, it further disclosesmeans to maximize the advantage of such a separate path throughprovision of a layer or coating of superhydrophobic material on the meshor membrane installed in the opening to contain the contents of canister16.

The foregoing example is only one application of the arrangementdescribed. It is contemplated that open pore mesh screen or membranecoated with a superhydrophobic layer has numerous applications wherepassage of a gas through the open pore structure is facilitated even inthe presence of a liquid containing environment. Examples contemplatedinclude medical filtration or delivery systems, food processing,industrial filtration and other environments.

Variations and modifications of the foregoing are within the scope ofthe present invention. It is understood that the invention disclosed anddefined herein extends to all alternative combinations of two or more ofthe individual features mentioned or evident from the text and/ordrawings. All of these different combinations constitute variousalternative aspects of the present invention. The embodiments describedherein explain the best modes known for practicing the invention andwill enable others skilled in the art to utilize the invention. Theclaims are to be construed to include alternative embodiments to theextent permitted by the prior art.

1. A gas pervious barrier resistant to closure when subjected to anaqueous liquid, said barrier coated with a superhydrophobic coating. 2.A gas pervious barrier as claimed in claim 1 wherein saidsuperhydrophobic coating comprises amorphous silicon and a polymer thatdoes not contain fluorine or per-fluoro compounds.
 3. A gas perviousbarrier as claimed in claim 2 wherein said coating has a thickness ofless than 200 nanometers.
 4. A gas pervious barrier as claimed in claim1 wherein said coating has a water droplet contact angle of at least150°.
 5. A gas pervious barrier as claimed in claim 4 wherein saidcoating has a water droplet roll-off angle of less than 10°.
 6. A gaspervious barrier as claimed in claim 1 wherein said barrier comprises anopen pore mesh.
 7. A gas pervious barrier as claimed in claim 6 whereinsaid open pore mesh has a mesh size exceeding ten (10) microns.
 8. A gaspervious barrier as claimed in claim 2 wherein said barrier comprises anopen pore mesh.
 9. A gas pervious barrier as claimed in claim 8 whereinsaid open pore mesh has a mesh size exceeding ten (10) microns.
 10. Agas pervious barrier as claimed in claim 3 wherein said barriercomprises an open pore mesh.
 11. A gas pervious barrier as claimed inclaim 10 wherein said open pore mesh has a mesh size exceeding ten (10)microns.
 12. A gas pervious barrier as claimed in claim 4 wherein saidbarrier comprises an open pore mesh.
 13. A gas pervious barrier asclaimed in claim 12 wherein said open pore mesh has a mesh sizeexceeding ten (10) microns.
 14. A gas pervious barrier as claimed inclaim 5 wherein said barrier comprises an open pore mesh.
 15. A gaspervious barrier as claimed in claim 14 wherein said open pore mesh hasa mesh size exceeding ten (10) microns.
 16. A gas pervious barrier asclaimed in claim 1 wherein said barrier is a membrane.
 17. A gaspervious barrier as claimed in claim 2 wherein said barrier is amembrane.
 18. A gas pervious barrier as claimed in claim 3 wherein saidbarrier is a membrane.
 19. A canister comprising: a housing having afluid inlet and a fluid outlet; a filter medium housed within saidcanister; a separate passage for egress of a gaseous medium; a gaspervious barrier, said barrier coated with a superhydrophobic layer. 20.A canister as claimed in claim 19 wherein said superhydrophobic coatingcomprises amorphous silicon and a polymer that does not contain fluorineor per-fluoro compounds.
 21. A canister as claimed in claim 20 whereinsaid coating has a thickness of less than 200 nanometers.
 22. A canisteras claimed in claim 19 wherein said coating has a water droplet contactangle of at least 150°.
 23. A canister as claimed in claim 22 whereinsaid coating has a water droplet roll-off angle of less than 10°.
 24. Acanister as claimed in claim 19 wherein said barrier comprises an openpore mesh.
 25. A canister as claimed in claim 24 wherein said open poremesh has a mesh size exceeding ten (10) microns.